Hydraulic machines such as, for example, dozers, loaders, excavators, motor graders, and other types of heavy equipment use one or more hydraulic actuators to accomplish a variety of tasks. These actuators are fluidly connected to a pump on the machine that provides pressurized fluid to chambers within the actuators. As the pressurized fluid moves into or through the chambers, the pressure of the fluid acts on hydraulic surfaces of the chambers to affect movement of the actuator and a connected work tool. When the pressurized fluid is drained from the chambers it is returned to a low pressure sump on the machine.
One problem associated with this type of hydraulic arrangement involves starting or operation of the machine when temperatures are low. Specifically, if the fluid used to move the actuators and/or associated valves is too cold, operation of the machine can become unpredictable and sluggish. In addition, cold operation or improper warming of the machine's components could result in damage to the machine. Thus, a warmup procedure may be useful prior to operation of the machine and the work tool.
One such warmup procedure is described in U.S. Pat. No. 5,410,878 (the '878 patent) issued to Lee et al. on May 2, 1995. Specifically, the '878 patent describes a hydraulic system equipped with an engine and a hydraulic pump driven by the engine and controlled by a microcomputer. The hydraulic system also includes a hydraulic actuator operated by pressurized oil discharged from the hydraulic pump, a valve disposed between the hydraulic pump and the hydraulic actuator, a first temperature sensor configured to detect a temperature of a lubricant oil within the engine, a second temperature sensor configured to detect a temperature of a cooling water within the engine, and a third temperature sensor configured to detect a temperature of the oil pressurized by the hydraulic pump.
During operation of the hydraulic system of the '878 patent, the microcomputer monitors the temperatures of the lubricant oil, the cooling water, and the pressurized oil to determine if warmup is necessary. When warmup is necessary, the microcomputer increases a rotational speed of the engine to a predetermined rotational speed, and then slowly adjusts a discharge oil amount and a pressure of the hydraulic pump and the valve until a load on the engine reaches a predetermined amount. The microcomputer continues to monitor the lubricant oil, cooling water, and pressurized oil temperatures and, after these temperatures reach predetermined values, operation of the engine, the pump, and the valve is returned to a low-idling operation.
Although the hydraulic system and method disclosed within the '878 patent may be helpful in warming a hydraulic system, the benefit thereof may be minimal. Specifically, although the fluid within the hydraulic system may be sufficiently warmed, the associated valves may remain too cold for proper operator or be heated at a rate that results in sticking or damage of the valves.
The disclosed machine control system is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.